Recently, some works have used subword units to translate instead of words.
In Sennrich, the rare and some unknown words are encoded as subword units with the Byte Pair Encoding (BPE) method.
The authors show that this can also generate words which are unseen at training time.
As an extreme case, the character-level neural machine translation has been presented in several works [1]}, [2]}, [3]} and showed very promising results.
